Logging to temporary directory in a cross-platform manner

Question

I have an application for which log4j logging is configured in a log4j.properties file. Currently, this application runs on UNIX and creates a log file in /tmp. This application needs to run on Windows, and on that platform I would like for it to select the correct temporary directory, which I believe is C:\temp.

How can I change my log4j.properties file to make this happen? Do I need to switch to using an XML configuration file?

Answer 1

I think you would just use ${java.io.tmpdir} in place of a hard-coded path.

Answer 2

As of Log4J v1.2.14, I was able to use this in both a log4j.xml file as well as a log4j.properties file. There was some discussion on the web that variables wouldn't parse in the DOMReader, but they do as of this version of log4j.

<appender name="rolling_file_appender_ourapp" class="org.apache.log4j.RollingFileAppender">
    <param name="File" value="${user.home}/.mycompany/OurApp.log" />
    <param name="Append" value="false" />
    <param name="MaxFileSize" value="10MB" />
    <param name="MaxBackupIndex" value="3" />
    <layout class="org.apache.log4j.PatternLayout">
        <param name="ConversionPattern" value="%d | %-5p | %c | %m | %t | %x %n" />
    </layout>
</appender>

or

log4j.appender.rfile=org.apache.log4j.FileAppender
log4j.appender.rfile.layout=org.apache.log4j.PatternLayout
log4j.appender.rfile.Append=false
log4j.appender.rfile.layout.ConversionPattern=%d [%p] %c %m%n
log4j.appender.rfile.File=${user.home}/.mycompany/OurApp.log